Basically male and female brains (no accounting yet for masculinized or feminized brains due to in-utero hormone loads) react differently to contempt (which relates to social hierarchy) and disgust (relating to ideals of physical purity). The reaction also varied according to gender of the face being viewed.

While the fMRI studies supported the hypothesis that male brains would be activated more strongly by contemptuous expressions (in line with the idea that males are more interested in pecking orders), there was also evidence that female brains are more strongly activated by expressions of disgust.

What was interesting, and will doubtless get the tabloid pundits jabbering without appropriate caveats, is the evidence that female brains are more affected by contemptuous expressions if those expressions were exhibited by male faces rather than female faces, while males are more affected by male faces expressing disgust than female faces.

From the abstract/intro:

In addition, the effect of stimulus sex differed for men versus women. Specifically, women showed stronger responses to male contemptuous faces (as compared to female expressions), in the insula and middle frontal gyrus.

From deeper in the body of the paper:

This analysis primarily showed that, for women, contemptuous male faces elicited more brain activation, with significant clusters in the insula, bilaterally, and right middle frontal gyrus. For disgust, men displayed more activation to male as compared to female faces in the left claustrum/insula.

Oh dear. So this could explain why males stereotypically pay little heed to a woman saying "that’s disgusting… don’t fart at the dinner table", while females stereotypically feel more put-upon if a male (rather than a female) is contemptuous towards them.

Mind you, this is talking about neuronal activation, not the feeling elicited in the mind. For example, a male might need more neuronal activation to register the same level of feeling about contempt (although this goes against the hypotheses that prompted the study – and I cannot make any judgement about activation versus sensation for either gender or either type of expression).

As I said, this is something that needs further investigation, but it does raise questions about the "eye of the beholder" guidelines for dealing with facial expressions perceived as "offensive".

However, even without more experimentation and analysis, expect this information to be used during the development of advertisements directed primarily at one gender.